Simply Science: All about lightning

GOLDEN VALLEY, Minn. - With this year's early start to spring, we've already heard some serious rumbles of thunder across the state and we've even had some severe weather warnings. With those thunderstorms, of course, comes lightning. Lightning is all thanks to electrical charges that build up within a storm cloud and near the earth surface.

Within a storm cloud, the negative ions cluster toward the base of the cloud and they are attracted to the positively charged surface of the earth. Because positive charges repel each other, the positive ions in a cloud rise away from the surface.

When the buildup of charges becomes great enough, positive ions from the earth's surface flow upward to neutralize the negative ions in the cloud base. This is lightning. The flash you see is this flow of ions. Thunder is the sound that accompanies this giant spark. Lightning within a cloud follows the same process.

Here in Minnesota, each square mile sees one to two ground lightning strikes per year. Thanks to more heat and more moisture, the Gulf Coast and southern Atlantic coast see the most lightning strikes at 8 to 16 per square mile per year.

Lightning and thunder happen at the same time but because sound travels slower than light, we hear the thunder after we see the lightning. We can use this to calculate how far away a storm is. When you see lightning, count the seconds until you hear the thunder. Divide that number by five and you get the distance from you to the storm in miles.

Lightning is one of the most deadly forces of nature, killing over 50 Americans each year. It's important to remember a few rules before, during and after a thunderstorm:

• Inside your house it's important to keep off wired electronics.

• If your house is struck, the electricity flows through the outlets and into your device.

• You're safe in a car. The metal parts of the car direct the electric current around you.

• You're not safe in water. Even in a small underground pool, the electricity can flow through connected underground pipes into your own pool from a strike far away.

• If you can hear the thunder, you are close enough to the storm to be struck by lightning.